In U.S. Pat. No. 4,108,002 of Charles L. Rowe et al, a disposable thermometer is disclosed which comprises essentially a molded plastic thermometer. The thermometer utilizes a layer of gas impervious, rigid material to effectively prevent gaseous diffusion into the capillary bore of the thermometer thereby to maintain a preselected vacuum condition in the thermometer, and maintain dimensional stability thereby to maintain high accuracy in the temperature indication use thereof. The wall thickness of the core tube, as disclosed therein, is relatively small with the outer synthetic resin jacket having a substantially greater wall thickness. As an illustrative thickness, the core tube was disclosed as having a wall thickness of approximately 0.20". The patent further disclosed that the synthetic resin portion could be molded in place in forming the low cost disposable thermometer.
Additional background art may be seen in the references cited in said Rowe et al patent. Illustratively, as further background art, another related structure is disclosed in U.S. Pat. No. 2,651,203 of Anthony H. Lamb, wherein a complete glass thermometer is disposed within a tube of transparent plastic. Lamb teaches that the plastic define a housing for the thermometer rather than define the outer jacket portion of the thermometer itself.
Gerald J. Coben discloses, in U.S. Pat. No. 3,490,287, a rectal thermometer wherein a plastic coating covers the entire thermometer and bulb.
Frederick J. Margolis discloses, in U.S. Pat. No. 2,712,237, a clinical thermometer wherein a metallic tube extends into and sealingly engages the bore of the glass tube of the thermometer. The metal tube is provided with a constriction forming a part of the bore. The constriction appears in the form of an indentation upon the outer surface of the tube and the material of the glass tube effectively keys into the indentation.